You can always create a script that would lower everybody's disposition towards you depending on your sting level.
Well yes thats will work, but token scripting will take more resources then changing of personality of one actor what will affect starting disposition of NPC, then dynamically change disposition of all NPC in cell for reaction on sting level of character by adding tokens to them, since dialogues not work anymore in MenuMode changes must be done in realtime, another thing before we can make scripted disease what will drain Personality and player can simple check stage at status tab or at attribute tab, if there will be no attributes to show this as well disease can be also axed from game because most of them affect attributes
http://www.uesp.net/wiki/Daggerfall:Diseases
http://www.uesp.net/wiki/Morrowind:Diseases
http://www.uesp.net/wiki/Oblivion:Disease
How player will able easy check level of %PCname sting?
And yes speechcraft is not affected by sting level, because you can have silver tongue and hideous appearance, as well you cant without personality what represent beauty and charisma make classy clothes for character.
Well http://www.youtube.com/watch?v=u2_8U2mSeDE but it never will look like this ridding in RDR or M&B if sufficient basis will be axed from game.